Method for calibrating driving amount of actuator configured to correct blurring of image taken by camera

ABSTRACT

A method for calibrating a driving amount of an actuator configured to correct blurring of an image taken by a camera attached to a device includes: taking an image of a mark by a camera to generate a first image, the mark reflecting a predetermined posture of the device; detecting a tilt of the mark in the first image; and based on the tilt of the mark, correcting the driving amount of the actuator that is predetermined according to a sensing result of a sensor for sensing a change in a posture of the device.

This nonprovisional application is based on Japanese Patent ApplicationNo. 2016-253390 filed on Dec. 27, 2016 with the Japan Patent Office, theentire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a technique for correcting the drivingamount of an actuator for correcting blurring of an image taken by acamera.

Description of the Background Art

Conventionally, various techniques for correcting blurring of an imagetaken by a camera have been proposed. For example, Japanese PatentLaying-Open No. 2016-173517 discloses an image blurring correctiondevice configured to “temperature-correct, among the motor controlamounts applied during correction of image blurring, (i) themovement-control amount with the first correction coefficient, and (ii)the hold-control amount used for holding a blurring correction mechanism110 in the center position with the second correction coefficient” (see“Abstract”).

SUMMARY OF THE INVENTION

In recent years, a camera module is mounted in various devices includinga mobile phone terminal, a tablet terminal, and the like. Also, ascameras have been increased in resolution and rendered moremultifunctional, the number of components mounted in such an informationprocessing terminal has also been increased. Meanwhile, the users arestrongly demanding to reduce the weight of the information processingterminal. Thus, the technique for reducing the size of a camera modulehas been required.

The present disclosure has been made in order to solve theabove-described problems. An object in a certain aspect is to provide atechnique allowing a reduction of the number of components mounted in acamera module attached to an information processing terminal equippedwith a sensor capable of sensing a posture.

Other problems and new characteristics will become apparent from thedescription of the present specification and the accompanying drawings.

According to an embodiment, a method for calibrating a driving amount ofan actuator configured to correct blurring of an image taken by a cameraattached to a device is provided. The device includes a sensor forsensing a change in a posture of the device. The above-described methodincludes: taking an image of a mark by a camera to generate a firstimage, the mark reflecting a predetermined posture of the device;detecting a tilt of the mark in the first image; and correcting adriving amount of an actuator based on the tilt of the mark, the drivingamount being predetermined according to a sensing result of the sensor.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram illustrating the configuration of an informationprocessing terminal according to the related art.

FIG. 1B is a diagram illustrating the configuration example of aninformation processing terminal according to an embodiment.

FIG. 2 is a diagram illustrating the configuration example of aninspection system according to the first embodiment.

FIG. 3A is a diagram illustrating that the axes of a gyro sensor and theaxes of an actuator coincide with each other.

FIG. 3B is a diagram illustrating that the axes of the gyro sensor andthe axes of the actuator deviate from each other.

FIG. 4 is a diagram illustrating a correction coefficient used forcorrecting the driving amount of the actuator.

FIG. 5 is a flowchart for illustrating the control flow in which anapplication processor (AP) calculates a correction coefficient,according to the first embodiment.

FIG. 6 is a diagram illustrating the control flow for a driverintegrated circuit (IC) to correct image blurring.

FIG. 7 is a diagram illustrating the degree of correcting image blurringaccording to the first embodiment.

FIG. 8 is a diagram illustrating the relation between an axis deviationangle θ1 and the amount of blurring.

FIG. 9 is a diagram illustrating a chart according to a modification.

FIG. 10 is a diagram illustrating a chart according to anothermodification.

FIG. 11 is a diagram illustrating deviations between the axes of theactuator and the axes of an image sensor.

FIG. 12A is a diagram illustrating that the axes of the actuator and theaxes of the image sensor coincide with each other.

FIG. 12B is a diagram illustrating that the axes of the actuator and theaxes of the image sensor deviate from each other.

FIG. 13 is a flowchart for illustrating the control flow in which an APcalculates a correction coefficient, according to the second embodiment.

FIG. 14 is a diagram illustrating the configuration example of aninspection system according to the third embodiment.

FIG. 15 is a diagram illustrating a method of detecting an axisdeviation angle according to the third embodiment.

FIG. 16 is a flowchart for illustrating the control flow in which an APcalculates a correction coefficient, according to the third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention will be hereinafter describedin detail with reference to the accompanying drawings. In the followingdescription, the same components are designated by the same referencecharacters. Names and functions thereof are also the same. Accordingly,the detailed description thereof will not be repeated. In addition,embodiments and modifications described later may be selectivelycombined as appropriate.

A. Introduction

FIGS. 1A and 1B each are a diagram for illustrating the outline of thetechnique according to an embodiment. FIG. 1A is a diagram illustratingthe configuration of an information processing terminal 100R accordingto the related art. FIG. 1B is a diagram illustrating the configurationexample of an information processing terminal 100 according to anembodiment.

Referring to FIG. 1A, information processing terminal 100R according tothe related art has a mainboard 110 and a camera module 120R. Mainboard110 is equipped with a gyro sensor 115 as an example of a motion sensorfor sensing a change in the posture of information processing terminal100R. The “posture” means the direction in which the device is directed(for example, the longitudinal direction, the lateral direction, and theheight direction of information processing terminal 100R). By way ofexample, gyro sensor 115 is configured to be capable of sensing theangular velocity about two axes in the longitudinal direction and thelateral direction of information processing terminal 100R. In anotheraspect, a geomagnetism sensor may be used as another example of thesensor for sensing a change in the posture of information processingterminal 100R. Camera module 120R includes a gyro sensor 130 for sensinga change in the posture of the module, and an actuator 140 forcorrecting blurring of an image (image blurring) taken by an imagingelement included in the module.

Gyro sensor 130 and actuator 140 are provided in the same camera module120R. Thus, during manufacturing of camera module 120R according to acertain aspect, gyro sensor 130 and actuator 140 are arranged in cameramodule 120R such that an X axis and a Y axis of gyro sensor 130 coincidewith an AX axis and an AY axis, respectively, extending in the directionin which actuator 140 is driven.

Information processing terminal 100R according to the related art drivesactuator 140 by the driving amount that is predetermined according tothe output (angular velocity) from gyro sensor 130 along the X axis andthe output from gyro sensor 130 along the Y axis. Thereby, the lens orthe sensor included in camera module 120R is caused to move so as tocompensate for image blurring. This predetermined driving amount is seton the precondition that the axes of gyro sensor 130 and the axes ofactuator 140 coincide with each other.

Information processing terminal 100R includes two gyro sensors thatmeasure different objects but have the same function. Thus, informationprocessing terminal 100R is increased in number of components as a wholedevice, which may lead to increased manufacturing cost.

Referring to FIG. 1B, information processing terminal 100 according tothe embodiment is different from information processing terminal 100Raccording to the related art in that camera module 120 does not includegyro sensor 130.

Information processing terminal 100 sets the driving amount of actuator140 according to the output from gyro sensor 115 attached to mainboard110 (information processing terminal 100). Thus, information processingterminal 100 according to the embodiment does not need to separatelyinclude gyro sensor 130 in camera module 120.

However, as shown in FIG. 1B, camera module 120 may be attached in thestate where it is tilted relative to information processing terminal100. This is because camera module 120 is not fastened to informationprocessing terminal 100 with screws or the like, but is attached toinformation processing terminal 100 in such a manner that this cameramodule 120 is wrapped in a shock-absorbing soft material. Accordingly, aplurality of information processing terminals 100 may be individuallydifferent in position (tilt) at which camera module 120 is attached toinformation processing terminal 100. On the other hand, gyro sensor 115is attached by soldering to information processing terminal 100 almostwithout being tilted.

Accordingly, when camera module 120 is attached in the state where it istilted relative to information processing terminal 100, the axes (X, Y)of gyro sensor 115 and the axes (AX, AY) of actuator 140 deviate fromeach other. In such a situation, when information processing terminal100 drives actuator 140 by the driving amount that is predeterminedaccording to the output from gyro sensor 115, image blurring cannot beaccurately corrected. This is because the predetermined driving amountis set on the precondition that the axes of gyro sensor 115 and the axesof actuator 140 coincide with each other, as described above.

Thus, information processing terminal 100 according to the embodimentdetects tilts of (the amount of deviation between) the axes of gyrosensor 115 provided outside camera module 120 and the axes of actuator140. Based on the detected tilts, information processing terminal 100corrects the driving amount of actuator 140 that is predeterminedaccording to the output from gyro sensor 115. Thereby, even if gyrosensor 115 provided outside camera module 120 is used for controllingactuator 140, information processing terminal 100 can accurately correctimage blurring. In the following, the details of control for correctingthe driving amount of actuator 140 will be described.

B. First Embodiment

(b1. Inspection System 200)

FIG. 2 is a diagram illustrating the configuration example of aninspection system 200 according to the first embodiment. Inspectionsystem 200 includes an information processing terminal 100, a jig 260, amonitor 270, and a test host 280.

Information processing terminal 100 includes a mainboard 110 and acamera module 120. Mainboard 110 includes an image memory 205, an imagesignal processor (ISP) 210, a gyro sensor 115, an application processor(AP) 215, a memory 217, and an interface (I/F) 220. I/F 220 iselectrically connected to image memory 205, ISP 210, gyro sensor 115, AP215, memory 217, and I/F 250 described later.

Information processing terminal 100 may be provided with a camera(camera module 120), and further provided with a sensor (for example, agyro sensor) capable of sensing the posture of a terminal and locatedoutside the camera. Information processing terminal 100 may be a smartphone, a tablet, a monitoring camera, a network camera, and otherterminals, for example.

ISP 210 performs image processing for the image data obtained by animage sensor 225, which will be described later. Image processing, forexample, includes: correction processing for an optical system;correction for scratches caused by variations of image sensor 225; andthe like.

Image memory 205 is configured to store the image data processed by ISP210. Gyro sensor 115 is configured to sense a change in the posture ofinformation processing terminal 100. Gyro sensor 115 is a sensor of avibration type, by way of example. In another aspect, gyro sensor 115may be a sensor of an optical type.

AP 215 executes checking firmware (F/W) 295, which will be describedlater, to determine the correction coefficient used for calibrating thedriving amount of actuator 140 that is predetermined according to theoutput from gyro sensor 115. Memory 217 stores a lookup table 219 usedfor determining this correction coefficient.

Camera module 120 includes an image sensor 225, a lens 230, actuators140X and 140Y, a driver integrated circuit (IC) 240, a memory 245 (forexample, a flash memory), and an I/F 250.

Image sensor 225 includes a plurality of photoelectric conversionelements arranged in two directions that are orthogonal to each other.Also, image sensor 225 is configured to generate image data.

Actuator 140X is configured to be capable of driving lens 230 in the AXdirection. Actuator 140Y is configured to be capable of driving lens 230in the AY direction. Actuators 140X and 140Y will be hereinaftercollectively referred to as an “actuator 140”. Actuator 140 isconfigured to correct image blurring by moving lens 230 (lens shiftscheme).

In another aspect, actuator 140 may be configured to correct imageblurring by moving image sensor 225 in place of lens 230 (sensor shiftscheme).

Driver IC 240 controls the amount of driving lens 230 by actuator 140.Based on the output from gyro sensor 115, driver IC 240 drives lens 230so as to correct image blurring in image sensor 225.

Memory 245 stores correction coefficients (sin θ1, cos θ1) used forcorrecting the driving amount by actuator 140 that is predeterminedaccording to the output from gyro sensor 115.

I/F 220 and I/F 250 each are implemented using I2C (registeredtrademark), MIPI (registered trademark) (Mobile Industry ProcessorInterface), and other terminals.

Jig 260 fixes information processing terminal 100 in a predeterminedposture. Gyro sensor 115 is attached to mainboard 110 such that the Xaxis and the Y axis of the sensor coincide with the major axis and theminor axis, respectively, of information processing terminal 100.

Monitor 270 is configured to display a chart 275. Chart 275 functions asa mark reflecting the predetermined posture of information processingterminal 100. By way of example, chart 275 has a cross shape includingstraight lines extending along the X axis and the Y axis of gyro sensor115.

Test host 280 includes a microcomputer 285 and a memory 290. Memory 290functions as a nonvolatile storage device, for example. Memory 290stores checking F/W (firmware) 295.

In a certain aspect, test host 280 may transfer checking F/W 295 tomemory 217. AP 215 may read checking F/W 295 from memory 217 onto arandom access memory (RAM) (not shown) or the like, and execute thischecking F/W 295.

(b2. Axis Deviation Between Gyro Sensor 115 and Actuator 140)

FIGS. 3A and 3B each are a diagram illustrating deviations between theaxes of gyro sensor 115 and the axes of actuator 140. FIG. 3A is adiagram illustrating that the axes of gyro sensor 115 and the axes ofactuator 140 coincide with each other. FIG. 3B is a diagram illustratingthat the axes of gyro sensor 115 and the axes of actuator 140 deviatefrom each other.

In the first embodiment, the directions in which a plurality ofphotoelectric conversion elements forming image sensor 225 are arrangedcorrespond to the axis directions of actuator 140 (that is, the AXdirection and the AY direction).

In examples shown in FIGS. 3A and 3B, image sensor 225 takes an image ofchart 275 displayed on monitor 270 in the state where informationprocessing terminal 100 is fixed to jig 260.

In FIG. 3A, the directions in which the bars forming the cross shape ofchart 275 extend correspond to the axis directions of image sensor 225.As described above, the directions in which the bars forming the crossshape of chart 275 extend correspond to the axis directions (the X axisand the Y axis) of gyro sensor 115. Then, the axis directions of imagesensor 225 correspond to the axis directions (the AX axis and the AYaxis) of actuator 140. In other words, in the example shown in FIG. 3A,the axis directions (the AX axis and the AY axis) of actuator 140correspond to the axis directions (the X axis and the Y axis) of gyrosensor 115.

In a certain aspect, based on the image including chart 275 taken byimage sensor 225, AP 215 determines whether the axis directions ofactuator 140 correspond to the axis directions of gyro sensor 115 ornot.

AP 215 performs edge processing for an image to thereby detect chart275. AP 215 further specifies the coordinates of representative pointsP1 and P2 in chart 275. By way of example, representative points P1 andP2 are defined as ends of a straight line extending along the Y axis.When the positions of representative points P1 and P2 coincide with eachother in the AX direction, AP 215 may determine that the axis directionsof actuator 140 coincide with the axis directions of gyro sensor 115.

In FIG. 3B, the directions in which the bars forming a cross shape ofchart 275 extend do not coincide with (are tilted relative to) the axisdirections of image sensor 225. In a certain aspect, AP 215 derivesdifference information (α, β) about the coordinates of representativepoints P1 and P2. Based on this difference information, AP 215calculates a tilt angle θ1 of chart 275 relative to each axis directionof image sensor 225. More specifically, AP 215 computes a tan (arctangent) (β/α) to calculate an angle θ1.

As described above, the directions in which the bars forming the crossshape of chart 275 extend correspond to the axis directions (the X axis,the Y axis) of gyro sensor 115. Then, the axis directions of imagesensor 225 correspond to the axis directions (the AX axis, the AY axis)of actuator 140. In other words, tilt angle θ1 of chart 275 relative toone axis direction of image sensor 225 shows an angle formed between oneaxis direction of gyro sensor 115 and one axis direction of actuator 140(that is, an axis deviation angle).

FIG. 4 is a diagram illustrating the correction coefficient used forcorrecting the driving amount of actuator 140. In the example shown inFIG. 4, the axes (X, Y) of gyro sensor 115 deviate by an angle θ1 fromthe axes (AX, AY) of actuator 140.

As described above, when actuator 140 is driven by the driving amountthat is predetermined according to the output from gyro sensor 115 inthe state where these axes deviate from each other, image blurringcannot be accurately corrected. This is because the predetermineddriving amount is set on the precondition that the axes of gyro sensor115 and the axes of actuator 140 coincide with each other.

Thus, based on axis deviation angle θ1, AP 215 determines the correctioncoefficient used for correcting the predetermined driving amount ofactuator 140.

Referring to FIG. 4, the AX-axis component is a value obtained bysubtracting the value, which is obtained by multiplying the Y-axiscomponent by sin θ1, from the value, which is obtained by multiplyingthe X-axis component by cos θ1. The AY axis component is a valueobtained by adding the value, which is obtained by multiplying theX-axis component by sin θ1 and the value, which is obtained bymultiplying the Y-axis component by cos θ1. In other words, when sin θ1and cos θ1 are fixed, the output from gyro sensor 115 can be convertedinto each axis direction of actuator 140. Thus, based on axis deviationangle θ1, AP 215 determines correction coefficients sin θ1 and cos θ1.

AP 215 outputs the determined correction coefficients to camera module120 through I/F 220. Camera module 120 stores these correctioncoefficients in memory 245.

Driver IC 240 uses the correction coefficients stored in memory 245 tocorrect the driving amount of the actuator that is predeterminedaccording to the output from gyro sensor 115. More specifically, driverIC 240 adds or subtracts the value multiplied by each correctioncoefficient to or from the predetermined driving amount (the X-axiscomponent and the Y-axis component), thereby converting the drivingamount into each axis direction of actuator 140.

(b3. Control Flow for Calculating Correction Coefficient)

FIG. 5 is a flowchart for illustrating the control flow in which AP 215calculates a correction coefficient, according to the first embodiment.The process executed in steps S520 to S560 shown in FIG. 5 isimplemented by AP 215 executing checking F/W 295. In another aspect,some or all of the process may be executed by a circuit element andother hardware.

In step S510, information processing terminal 100 downloads checking F/W295 from test host 280, and stores the downloaded checking F/W 295 inmemory 217. AP 215 reads checking F/W 295 from memory 217 and executesthis checking F/W 295.

In step S520, through I/F 220 and I/F 250, AP 215 outputs an instructionto image sensor 225 to take an image. Thereby, image sensor 225generates image data including chart 275 configured to allow the axisdirections of gyro sensor 115 to be specified. Image sensor 225 outputsthe generated image data to ISP 210. ISP 210 performs prescribed imageprocessing for the image data, and stores the image-processed image datain image memory 205.

In step S530, AP 215 performs edge processing for the image data storedin image memory 205, to detect chart 275. AP 215 further specifies thecoordinates of two representative points from the detected chart 275.

In step S540, AP 215 calculates a tilt angle θ1 (axis deviation angleθ1) of chart 275 based on the specified coordinates of two points.

In step S550, AP 215 refers to lookup table 219 stored in memory 217 todetermine correction coefficients sin θ1 and cos θ1 for axis deviationangle θ1. These correction coefficients are values used for calibratingthe driving amount of actuator 140 that is predetermined according tothe output from gyro sensor 115. As shown in FIG. 5, lookup table 219holds the angles, the sine function values and the cosine functionvalues for the angles in association with one another.

In another aspect, AP 215 may be configured to calculate correctioncoefficients sin θ1 and cos θ1 for axis deviation angle θ1, not by usinglookup table 219, but by using the application for calculating knowntrigonometric functions.

In step S560, AP 215 outputs the specified correction coefficients tocamera module 120. Camera module 120 stores the inputted correctioncoefficients in memory 245.

(b4. Control Flow for Correcting Image Blurring)

FIG. 6 is a diagram illustrating the control flow for driver IC 240 tocorrect image blurring. Referring to FIG. 6, driver IC 240 includessubtractors 605, 640, 655, offsets 610, 660, high pass filters (HPF)615, 665, integrators 620, 670, sensitivity adjustment units 625, 675,cos multipliers 630, 685, sin multipliers 635, 680, and an adder 690.

Subtractor 605 subtracts an offset voltage, which is output from offset610, from the voltage value showing the angular velocity about theX-axis direction that is output from gyro sensor 115. The output fromoffset 610 (and offset 660) corresponds to the output from gyro sensor115 in the stationary state, and is set in advance in the manufacturingstage. In another aspect, the output from offset 610 may vary accordingto temperature. Due to the effects of offset 610 and subtractor 605, thetime period (convergence time) required to remove the DC offsetcomponent in an HFP 615 described later may be shortened.

Then, HPF 615 removes the DC offset component for a reference voltagefrom the signal output from subtractor 605. Integrator 620 integratesthe signal input from HPF 615. Sensitivity adjustment unit 625 performsthe process of amplifying the signal output from integrator 620.Sensitivity adjustment unit 625 outputs the amplified signal to a cosmultiplier 630 and a sin multiplier 635.

The angular velocity about the Y-axis direction, which is output fromgyro sensor 115, is also subjected to the same process as describedabove. Accordingly, the description about the processes performed bysubtractor 655, offset 660, HPF 665, integrator 670, and sensitivityadjustment unit 675 will not be repeated.

Then, cos multiplier 630 outputs, to subtractor 640, the value obtainedby multiplying the output from sensitivity adjustment unit 625 by acorrection coefficient cos θ1 stored in memory 245. Then, sin multiplier635 outputs, to adder 690, the value obtained by multiplying the outputfrom sensitivity adjustment unit 625 by a correction coefficient sin θ1.

Then, sin multiplier 680 outputs, to subtractor 640, the value obtainedby multiplying the output from sensitivity adjustment unit 675 bycorrection coefficient sin θ1. Then, cos multiplier 685 outputs, toadder 690, the value obtained by multiplying the output from sensitivityadjustment unit 675 by correction coefficient cos θ1.

Subtractor 640 outputs, to actuator 140X, the value obtained bysubtracting the output of sin multiplier 680 from the output of cosmultiplier 630. Adder 690 outputs, to actuator 140Y, the value obtainedby adding the output of sin multiplier 635 and the output of cosmultiplier 685.

According to the above description, camera module 120 for which acorrection coefficient is set by inspection system 200 can accuratelycorrect image blurring by using gyro sensor 115 disposed outside cameramodule 120. Thus, according to the inspection method by inspectionsystem 200 (checking F/W 295), the number of components in informationprocessing terminal 100 can be reduced, so that information processingterminal 100 can be reduced in size, weight and manufacturing cost.

Furthermore, the inspection method according to inspection system 200allows omission of the process of adjusting the sensitivity of gyrosensor 115 by applying vibration, which has been conventionallyperformed. Thus, according to this inspection method, the driving amountof the actuator may be calibrated at low cost without requiring avibration device.

In addition, in the above-mentioned method, calibration may be performedbased on the correct trigonometric function values by referring to thelookup table. Thus, according to the above-mentioned method, imageblurring can be accurately corrected.

FIG. 7 is a diagram illustrating the degree of correcting image blurringaccording to the first embodiment. In FIG. 7, the horizontal axis showsthe degree of applying vibration (angle) while the vertical axis showsthe amount of blurring. The vibration angle shows the angle at whichinformation processing terminal 100 tilts in the time period (shuttertime) during which image sensor 225 takes in the quantity of light. InFIG. 7, axis deviation angle θ1 between one axis of gyro sensor 115 andone axis of actuator 140 is assumed to be 3 degrees. The amount ofblurring shows the degree (pixel) of broadening of the photographicsubject due to blurring.

As shown in FIG. 7, by the method of correcting image blurring (controlshown in FIG. 6) according to the first embodiment, the amount ofblurring can be reduced as compared with the case where blurring is notcorrected. For example, when vibration of 0.7 degree is applied, theamount of blurring is reduced from 1.5 pixel to less than 1.0 pixel.

(b4. Modification 1)

In the above-described example, AP 215 is configured to determine thecorrection coefficients for axis deviation angle θ1 by referring tolookup table 219. However, lookup table 219 has relatively large datavolume, so that this lookup table 219 may require a relatively largearea in memory 217 of information processing terminal 100. On the otherhand, when the correction coefficients are determined by computation ofthe trigonometric functions, a computation engine with high performance(the throughput of AP 215) may be required. Thus, AP 215 according tothe modification calculates correction coefficients sin θ1 and cos θ1based on axis deviation angle θ1 by linear approximation.

FIG. 8 is a diagram illustrating the relation between axis deviationangle θ1 and the amount of blurring. In FIG. 8, the angle of applyingvibration is assumed to be 1.5 degrees. A distribution 810 shows theamount of blurring in the Y direction with respect to axis deviationangle θ1. A distribution 820 shows the amount of blurring in the Xdirection with respect to axis deviation angle θ1. A straight line 830represents a line obtained by linear approximation of distribution 810.A straight line 840 represents a line obtained by linear approximationof distribution 820.

As shown in FIG. 8, in a region 850 in which axis deviation angle θ1 isless than 3 degrees, there are almost no errors between distribution 810and straight line 830, and also between distribution 820 and straightline 840. In most cases, axis deviation angle θ1 caused by attachment ofcamera module 120 to information processing terminal 100 is also lessthan 3 degrees.

Accordingly, the information processing terminal according to themodification stores, in memory 217, the linear approximate expression ofthe sine function value and the linear approximate expression of thecosine function value in a small angle (for example, less than 3degrees). After axis deviation angle θ1 is detected, AP 215 (checkingF/W 295) according to the modification calculates correctioncoefficients sin θ1 and cos θ1 according to these linear approximateexpressions.

In view of the above description, by the inspection method according tothe modification, a correction coefficient can be simply calculatedwithout requiring lookup table 219. Thus, by the inspection methodaccording to the modification, the manufacturing cost for informationprocessing terminal 100 can be further reduced as compared with theinspection method according to the first embodiment.

(b5. Modification 2)

In the above-described example, chart 275 has a cross shape formed bybars specifying the axes of gyro sensor 115, but the shape of chart 275is not limited to a cross shape. Chart 275 only has to have a shape thatcan specify axis deviation angle θ1 between each axis of gyro sensor 115and each axis of actuator 140.

FIG. 9 is a diagram illustrating a chart 275A according to amodification. FIG. 10 is a diagram illustrating a chart 275B accordingto a modification. As shown in FIG. 9, axis deviation angle θ1 may bespecified also by chart 275A formed by combining a plurality of circles.Furthermore, as shown in FIG. 10, axis deviation angle θ1 may bespecified also by chart 275B formed by a rectangular shape defining oneof the axis directions of gyro sensor 115.

(b6. Modification 3)

In the above-described example, information processing terminal 100 isconfigured to be fixed to jig 260. In another aspect, the inspectionsystem further includes a camera for taking an image of informationprocessing terminal 100. AP 215 specifies the outside-diameter line ofinformation processing terminal 100 by image processing, and specifiesthe major axis (that is, the X axis) and the minor axis (that is, the Yaxis) of information processing terminal 100. Thereby, chart 275extending in the X-axis direction and the Y-axis direction may bedisplayed on monitor 270. In this case, the inspection system does notrequire jig 260 for fixing information processing terminal 100 in apredetermined posture.

(b7. Modification 4)

In the above-described example, chart 275 is configured to be displayedon monitor 270. In another aspect, chart 275 may be formed not onmonitor 270 but on a recording medium (a sheet of paper, and the like).

C. Second Embodiment

(c1. Axis Deviation Between Actuator 140 and Image Sensor 225)

FIG. 11 is a diagram illustrating deviations between the axes ofactuator 140 and the axes of image sensor 225. The axes of image sensor225 extend in the directions in which a plurality of photoelectricconversion elements forming image sensor 225 are arranged.

In the first embodiment, it is assumed that the axes (AX, AY) ofactuator 140 and the axes (IX, IY) of image sensor 225 coincide witheach other. However, these axes may deviate from each other depending onthe accuracy of attaching actuator 140 and image sensor 225 duringmanufacturing of camera module 120.

In the method of correcting the driving amount of actuator 140 accordingto the first embodiment, the output from gyro sensor 115 is convertedinto each axis direction of image sensor 225. Accordingly, by thismethod, image blurring cannot be accurately corrected if the axes ofactuator 140 and the axes of image sensor 225 deviate from each other.

Thus, in the inspection method according to the second embodiment, thedriving amount of actuator 140 that is predetermined according to theoutput from gyro sensor 115 is corrected in consideration of axisdeviation angle θ2 between each axis of actuator 140 and each axis ofimage sensor 225.

In addition, the configuration of the inspection system according to thesecond embodiment is the same as the configuration of inspection system200 according to the first embodiment. Accordingly, the detaileddescription of the configuration of the inspection system will not berepeated.

FIGS. 12A and 12B each are a diagram illustrating the method forspecifying axis deviation angle θ2 between each axis of actuator 140 andeach axis of image sensor 225. FIG. 12A is a diagram showing that theaxes of actuator 140 and the axes of image sensor 225 coincide with eachother. FIG. 12B is a diagram showing that the axes of actuator 140 andthe axes of image sensor 225 deviate from each other.

In FIGS. 12A and 12B, after image sensor 225 takes an image of chart 275to generate the first image, driver IC 240 causes lens 230 to move inthe AX-axis direction of actuator 140. Then, image sensor 225 takes animage of chart 275 again to generate the second image.

In FIGS. 12A and 12B, a chart 1210 corresponds to chart 275 in the firstimage while a chart 1220 corresponds to chart 275 in the second image.

Referring to FIG. 12A, when the axes of actuator 140 and the axes ofimage sensor 225 coincide with each other, the positions of chart 1210and chart 1220 along the IY direction before and after lens 230 is movedin the AX direction coincide with each other. On the other hand,referring to FIG. 12B, when the axes of actuator 140 and the axes ofimage sensor 225 deviate from each other, the positions of chart 1210and chart 1220 deviate from each other in the IY direction.

Based on the amount of change in coordinates of a representative pointPos in chart 275, AP 215 (checking F/W) according to the secondembodiment may specify axis deviation angle θ2 between each axis ofactuator 140 and each axis of image sensor 225. By way of example,representative point Pos is defined as a cross point between thestraight line extending in the X axis and the straight line extending inthe Y axis.

AP 215 specifies the coordinates (N, M) of representative point Pos inchart 1210 included in the first image. Then, AP 215 specifies thecoordinates (N+γ, M+ω) of representative point Pos in chart 1220included in the second image. AP 215 further specifies the differenceinformation (γ, ω) between these coordinates, to calculate axisdeviation angle θ2 based on this difference information. Morespecifically, AP 215 computes a tan (ω/γ) to calculate axis deviationangle θ2.

(c2. Control Flow for Calculating Correction Coefficient)

FIG. 13 is a flowchart for illustrating the control flow in which AP 215calculates a correction coefficient, according to the second embodiment.The process executed in steps S1320 to S1390 shown in FIG. 13 isimplemented when AP 215 executes checking F/W according to the secondembodiment. In another aspect, some or all of the process may beexecuted by a circuit element and other hardware. In addition, byexecuting the process in steps S510 to step S550 in FIG. 5, AP 215 hasalready recognized axis deviation angle θ1 between each axis of gyrosensor 115 and each axis of actuator 140.

In step S1310, AP 215 downloads checking F/W according to the secondembodiment from test host 280, and stores the downloaded checking F/W inmemory 217. AP 215 reads checking F/W from memory 217, and executes thischecking F/W.

In step S1320, through I/F 220 and I/F 250, AP 215 outputs aninstruction to image sensor 225 to take an image. Thereby, image sensor225 takes an image of chart 275 and generates the first image. The firstimage is subjected to prescribed image processing by ISP 210 andthereafter stored in image memory 205.

In step S1330, AP 215 performs edge processing for the first image, andspecifies chart 1210. AP 215 further specifies the coordinates (N, M) ofrepresentative point Pos in chart 1210, and stores the coordinates inmemory 217 or a RAM (not shown).

In step S1340, through I/F 220 and I/F 250, AP 215 outputs aninstruction to driver IC 240 to move lens 230. Thereby, driver IC 240causes actuator 140X or 140Y to move lens 230 in the AX-axis directionor in the AY-axis direction.

In step S1350, AP 215 outputs an instruction to image sensor 225 to takean image. Thereby, image sensor 225 takes an image of chart 275 andgenerates the second image. The second image is stored in image memory205.

In step S1360, as in step S1330, AP 215 specifies the coordinates (N+γ,M+ω) of representative point Pos in chart 1220 included in the secondimage, and stores the data showing the specified coordinates in memory217 or a RAM (not shown).

In step S1370, based on the coordinates (N, M) of representative pointPos in the first image and the coordinates (N+γ, M+ω) of representativepoint Pos in the second image, AP 215 specifies the differenceinformation (γ, ω). AP 215 further calculates axis deviation angle θ2based on the difference information. In step S1380, AP 215 specifies thecorrection coefficient based on axis deviation angle θ2 and the alreadyspecified axis deviation angle θ1. More specifically, AP 215 determineswhether or not the direction (rotation direction) in which the axes ofimage sensor 225 deviate from the axes of gyro sensor 115 is the same asthe direction in which the axes of actuator 140 deviate from the axes ofimage sensor 225. If AP 215 determines that these axes deviate in thesame direction, AP 215 specifies the correction coefficient for an angle(θ1+θ2) from lookup table 219. On the other hand, if AP 215 determinesthat these axes deviate in different directions, AP 215 specifies thecorrection coefficient for an angle (θ1−θ2) from lookup table 219.

In step S1390, AP 215 outputs the specified correction coefficient tocamera module 120. Camera module 120 stores the inputted correctioncoefficient in memory 245.

In view of the above description, by the inspection method according tothe second embodiment, the driving amount of actuator 140 predeterminedaccording to the output from gyro sensor 115 can be calibrated also inconsideration of the axis deviations between the axes of actuator 140and the axes of image sensor 225. Thus, the inspection method accordingto the second embodiment allows more accurate correction of imageblurring as compared with the inspection method according to the firstembodiment.

D. Third Embodiment

In the inspection method according to the above-described embodiment,axis deviation angle θ1 (and θ2) is calculated based on the imageobtained by taking an image of the chart to thereby determine, based onthis axis deviation angle, the correction coefficient used forcorrecting the driving amount of actuator 140. In the inspection methodaccording to the third embodiment, information processing terminal 100is vibrated to thereby determine, based on the output from gyro sensor115 (vibration information) obtained at the time, the correctioncoefficient used for correcting the driving amount of actuator 140.

(d1. Inspection System 1400)

FIG. 14 is a diagram illustrating the configuration example of aninspection system 140 according to the third embodiment. Since theportions designated by the same reference characters in FIG. 2 are thesame as those in FIG. 2, the description thereof will not be repeated.

Inspection system 1400 is different from inspection system 200illustrated in FIG. 2 in that a vibration device 1410 is included, thatchecking F/W 1420 in place of checking F/W 295 is stored in memory 290,and that monitor 270 is not provided.

(d2. Axis Deviation Between Gyro Sensor 115 and Actuator 140)

FIG. 15 is a diagram illustrating a method of detecting the axisdeviation angle according to the third embodiment. In FIG. 15, thehorizontal axis shows time while the vertical axis shows the output fromgyro sensor 115 (the value obtained by A/D conversion of the voltage).FIG. 15 shows an example of the output from gyro sensor 115 obtainedwhen a vibration table 1410 is used to apply vibration to informationprocessing terminal 100 by 1 degree about the AX axis of actuator 140(in the yaw direction).

A curved line 1510 shows the output from gyro sensor 115 along the Xaxis (in the yaw direction). A curved line 1520 shows the output fromgyro sensor 115 along the Y axis (in the pitch direction). A curved line1530 shows the data obtained by performing filtering processing (forexample, smoothing processing) for curved line 1520. The X-axisdirection of gyro sensor 115 extends approximately in the same directionas the AX-axis direction of actuator 140.

When the axes (X, Y) of gyro sensor 115 and the axes (AX, AY) ofactuator 140 deviate from each other, the output from gyro sensor 115along the X axis is reduced with respect to vibration applied in the yawdirection. Furthermore, the output from gyro sensor 115 along the Y axisis generated.

In the inspection method according to the fourth embodiment, axisdeviation angle θ1 between each axis of gyro sensor 115 and each axis ofactuator 140 is calculated by utilizing the above-describedcharacteristics. More specifically, AP 215 calculates an amplitude 1540of curved line 1510, and an amplitude 1550 of curved line 1530. Then, AP215 calculates the ratio of amplitude 1550 to amplitude 1540. Then, AP215 computes a tan of the calculated ratio to calculate axis deviationangle θ1.

(d3. Control Flow for Calculating Correction Coefficient)

FIG. 16 is a flowchart for illustrating the control flow in which AP 215calculates a correction coefficient, according to the third embodiment.

In step S1610, AP 215 downloads checking F/W 1420 from test host 280,and stores the downloaded checking F/W 1420 in memory 217. AP 215 readschecking F/W from memory 217, and executes this checking F/W.

In step S1620, information processing terminal 100 fixed to vibrationdevice 1410 is vibrated in the AX-axis direction of actuator 140. Inanother aspect, information processing terminal 100 may be vibrated inthe AY-axis direction of actuator 140.

In step S1630, AP 215 enables gyro sensor 115 so as to obtain the output(vibration information) from gyro sensor 115. In step S1640, AP 215performs filtering processing (for example, smoothing processing) forthe vibration information.

In step S1650, AP 215 calculates the amplitude based on the vibrationinformation obtained after the filtering processing. More specifically,AP 215 calculates the amplitude of the vibration information along the Xaxis and the amplitude of the vibration information along the Y axis.

In step S1660, based on the ratio between the amplitude of the vibrationinformation along the X axis and the amplitude of the vibrationinformation along the Y axis, which are calculated in step S1650, AP 215calculates axis deviation angle θ1.

In step S1670, AP 215 refers to lookup table 219 stored in memory 217,to specify correction coefficients sin θ1 and cos θ1 for axis deviationangle θ1. These correction coefficients are values used for calibratingthe driving amount of actuator 140 that is predetermined according tothe output from gyro sensor 115.

In step S1680, AP 215 outputs the specified correction coefficients tocamera module 120. Camera module 120 stores the inputted correctioncoefficients in memory 245.

In view of the above description, by the inspection method according toinspection system 1400, the axis deviation angle between the gyro sensorand the actuator can be calculated using the vibration device.Generally, the vibration device is used for adjusting the sensitivity ofthe gyro sensor. Thus, this inspection method does not require newcapital investment, but employs the existing facility, thereby allowingcorrection (calibration) of the driving amount of actuator 140 that isrequired when gyro sensor 115 disposed outside camera module 120 isused.

In view of the above description, according to a certain embodiment, thedisclosed technical characteristics may be summarized as follows, forexample.

[Configuration]

(Configuration 1)

According to a certain embodiment, a method for calibrating a drivingamount of an actuator 140 configured to correct blurring of an imagetaken by a camera module 120 attached to an information processingterminal 100 is provided. Information processing terminal 100 includes agyro sensor 115 for sensing a change in the posture of informationprocessing terminal 100. This method includes: taking an image of achart 275 by an image sensor 225 to generate the first image, chart 275reflecting a predetermined posture of information processing terminal100 (step S520); detecting a tilt (axis deviation angle θ1) of chart 275in the first image (step S540); and based on the tilt of chart 275,correcting the driving amount of actuator 140 that is predeterminedaccording to the sensing result of gyro sensor 115 (steps S550 andS560).

(Configuration 2)

In (Configuration 1), chart 275 has a shape specifying the axisdirections (X, Y) of gyro sensor 115.

(Configuration 3)

In (Configuration 1), the tilt of chart 275 shows a tilt of the axis(AX, AY) of actuator 140 relative to the axis (X, Y) of gyro sensor 115.

(Configuration 4)

In (Configuration 1), camera module 120 includes an image sensor 225formed by an imaging element, and a lens 230 for forming an image oflight on image sensor 225. The above-described method further includes:after actuator 140 is caused to act on lens 230 or image sensor 225 fromthe state where the first image is taken, taking an image of chart 275by image sensor 225 to generate the second image (step S1340 and stepS1350); calculating a difference between the position of chart 275(1210) in the first image and the position of chart 275 (1220) in thesecond image (step S1370); and, based on the difference, correcting thedriving amount of actuator 140 that is predetermined according to thesensing result of gyro sensor 115 (step S1380).

(Configuration 5)

In (Configuration 1), correcting the driving amount of actuator 140includes: referring to a lookup table 219 including a memory (217)storing a correction value and a tilt associated with each other, tospecify a correction coefficient in accordance with the tilt of chart275; and, based on the specified correction coefficient, correcting thedriving amount of actuator 140 that is predetermined according to thesensing result of gyro sensor 115.

(Configuration 6)

In (Configuration 1), correcting the driving amount of actuator 140includes: referring to a relational expression between the correctionvalue and the tilt stored in memory (217), to specify a correctioncoefficient in accordance with the tilt of chart 275; and, based on thespecified correction coefficient, correcting the driving amount ofactuator 140 that is predetermined according to the sensing result ofgyro sensor 115.

(Configuration 7)

According to another embodiment, a method for calibrating a drivingamount of an actuator 140 configured to correct blurring of an imagetaken by a camera module 120 attached to an information processingterminal 100 is provided. Information processing terminal 100 includes agyro sensor 115 for sensing a change in the posture of informationprocessing terminal 100. The method includes: swinging informationprocessing terminal 100 having camera module 120 attached thereto in thedirection about the AX axis or the AY axis of actuator 140 (step S1620);during swinging of information processing terminal 100, detecting theamount of change in the output from gyro sensor 115 along (i) the X-axisdirection extending approximately in the same direction as a prescribedaxis and (ii) the Y-axis direction that is orthogonal to the X-axisdirection (step S1630); and, based on the ratio between the amount ofchange in the output from the gyro sensor along the X-axis direction andthe amount of change in the output from the gyro sensor along the Y-axisdirection, correcting the driving amount of actuator 140 that ispredetermined according to the sensing result of gyro sensor 115 (stepsS670 and S1680).

Although the embodiments of the present disclosure have been describedas above, it should be understood that the embodiments disclosed hereinare illustrative and non-restrictive in every respect. The scope of thepresent disclosure is defined by the terms of the claims, and isintended to include any modifications within the meaning and scopeequivalent to the terms of the claims.

What is claimed is:
 1. A method comprising: taking an image of a mark bya camera to generate a first image, the mark reflecting a predeterminedposture of a device to which the camera is attached; detecting a tilt ofthe mark in the first image; and correcting a driving amount of anactuator for correcting blurring of an image taken by the camera basedon the tilt of the mark, the driving amount being predeterminedaccording to a sensing result of a sensor for sensing a change in aposture of the device.
 2. The method according to claim 1, wherein thesensor includes a gyro sensor.
 3. The method according to claim 2,wherein the mark has a shape specifying an axis direction of the gyrosensor.
 4. The method according to claim 2, wherein the tilt of the markincludes a tilt of an axis of the actuator relative to an axis of thegyro sensor.
 5. The method according to claim 1, wherein the cameraincludes an image sensor configured by an imaging element, and a lensfor forming an image of light on the image sensor, the method furthercomprising: after causing the actuator to act on the lens or the imagesensor from a state where the first image is taken, taking an image ofthe mark by the camera to generate a second image; calculating adifference between a position of the mark in the first image and aposition of the mark in the second image; and based on the difference,correcting the driving amount of the actuator that is predeterminedaccording to the sensing result of the sensor.
 6. The method accordingto claim 1, wherein the correcting the driving amount of the actuatorincludes referring to a lookup table including a memory storing a tiltand a correction value that are associated with each other, to specify acorrection coefficient in accordance with the tilt of the mark; andbased on the specified correction coefficient, correcting the drivingamount of the actuator that is predetermined according to the sensingresult of the sensor.
 7. The method according to claim 1, wherein thecorrecting the driving amount of the actuator includes: referring to arelational expression between a tilt and a correction value stored in amemory, to specify a correction coefficient in accordance with the tiltof the mark; and based on the specified correction coefficient,correcting the driving amount of the actuator that is predeterminedaccording to the sensing result of the sensor.
 8. A method comprising:swinging a device having a camera attached thereto in a direction abouta prescribed axis of an actuator configured to correct blurring of animage taken by the camera; during swinging of the device, detecting anamount of change in an output from a gyro sensor for sensing a change ina posture of the device, the amount of change being defined along afirst direction extending in a direction that is approximately identicalto the prescribed axis, and along a second direction that is orthogonalto the first direction; and based on a ratio between the amount ofchange in the output from the gyro sensor along the first direction andthe amount of change in the output from the gyro sensor along the seconddirection, correcting a driving amount of the actuator that ispredetermined according to a sensing result of the gyro sensor.